1. Field of the Invention
The present invention relates generally to the recycle of wasted metal products and, more particularly, to the preparation of metal feedstock from wasted metal products such as, for example, metallic component parts of electric products including, for example, air conditioners or refrigerators.
2. Description of the Prior Art
In the conventional recycling practice, crushed pieces of a wasted metal product are first separated into ferrous and non-ferrous materials by the utilization of magnetism and the ferrous materials so separated are, without being further sorted, charged into a cupola to produce a ferrous feedstock. To feed the ferrous materials into the cupola, the ferrous material must be in the form of bricks of a size comparable to that of a refractory brick so that the ferrous materials will not be blown up by a hot blast within the cupola.
To prepare the ferrous bricks, the ferrous materials may be pressed together by the use of, for example, a press. However, if the ferrous materials include both sheet-shaped scraps, regardless of whether flat or deformed, and cast blocks, the cast blocks often render it difficult for the ferrous materials to be pressed into the ferrous bricks. Accordingly, the magnetically separated ferrous materials have been utilized only as a low-quality scrap.
In some case, the sheet-shaped ferrous scraps are further separated from the cast blocks and pressed together for reuse as a metal feedstock. The pressed iron scraps are fed into a melting furnace such as a cupola or an electric furnace. In that case, however, after feeding the metal feedstock into the furnace, a mixture of component adjusters such as carbon, silicon, manganese, phosphorus and/or sulfur must be fed into the furnace to adjust the concentration of impurities contained in the melt within the furnace. Those component adjusters must be mixed in a mixing ratio that is determined depending on the application for which the material recycled from the metal feedstock is intended to use. By way of example, the metal feedstock is to be eventually used as a material for component parts of an electric compressor to a type generally used in air-conditioner or refrigerators, the following compositions as shown in Table 1 is required.
Since these component adjusters are relatively light-weight, they tend to float in a top layer of the ferrous melt within the furnace. The component adjusters afloat on the top layer of the melt without being well mixed in the melt are apt to be oxidized and become dross. This brings about problems associated with low efficiency of utilization of the component adjusters and increase in quantity of dust. Further, there are problems in that feeding of the adjusters is hazardous and also in that an extra process of removing the dross is required.
It is accordingly an objective of the present invention to enable the metal feedstock to be efficiently and safely prepared from wasted metal products to recycle the metal products without the efficiency of utilization of the component adjusters being lowered.
Another objective of the present invention is to provide the metal feedstock which when fed into a cupola will neither fly nor break up during falling downwardly within the cupola.
For this purpose, the present invention provides a method of and an apparatus for making the metal feedstock from the wasted metal products. According to the present invention, the metal feedstock can be prepared from wasted metal products by crushing the metal products into pieces; magnetically separating the crushed pieces into sheet-shaped ferrous scraps and ferrous cast blocks; placing the ferrous cast blocks between the sheet-shaped ferrous scraps to make a sandwich structure; and pressing the sandwich structure to form the ferrous feedstock.
According to the present invention, the sheet-shaped scraps and the cast blocks are firmly bound together to form a heavy metal feedstock. The metal feedstock will not fly up in the cupola and is efficiently utilized as a casting material.
In a preferred embodiment of the invention, the magnetically separating step includes a first-separation step separating the sheet-shaped ferrous scraps, and a second-separation step separating the ferrous cast blocks. A magnetic flux density around the crushed pieces employed during the second-separation step is preferably set at a value higher than that that during the first-separation step. This relationship assists in improving the efficiency of recovery of iron pieces and reducing the content of copper in the resultant ferrous feedstock.
In another embodiment of the invention, after the magnetical separating step, the ferrous cast blocks smaller than a predetermined size may be further separated. Since the ferrous cast blocks larger than the predetermined size can be fed into the cupola without pressing process, that further separation improves a productivity of the metal feedstock.
A weight percentage of the sheet-shaped ferrous scraps in the sandwich structure is preferably greater than 60% to prevent disassembling of the resultant metal feedstock during falling in the cupola.
In a further embodiment of the invention, content adjusters may be mixed in the sandwich structure. This eliminates the hazardous process of adding the content adjuster to the melted iron in the cupola. By combining the content adjusters with the sandwich structure, the adjusters will sink in the melted iron and will not oxidized. Thus, mixing of the content adjusters can take place smoothly and the efficiency of utilization of the adjusters can be increased.
In a second aspect of the present invention, an apparatus for forming a metal feedstock from wasted metal products comprises:
first, second and third measuring means for measuring out an amount of iron pieces, wherein said first and second measuring means are for sheet-shaped ferrous scraps and said second measuring means is for ferrous cast blocks, said scraps and blocks being obtained by crushing waste metal products;
a third measuring means for measuring an amount of the sheet-shaped ferrous scraps;
transport means for successively transporting the sheet-shaped scraps, the cast blocks and the sheet-shaped scraps that have been measured by said first, second and third measuring means respectively;
a holding means for receiving and holding the sheet-shaped scraps, the cast blocks and the sheet-shaped scraps transported by said transport means; and
a pressing means for simultaneously pressing the sheet-shaped scraps, the cast blocks and the sheet-shaped scraps in said holding means to form a cast feedstock of a sandwich structure.
According to the apparatus of the present invention, a predetermined amount of sheet-shaped scraps and cast blocks are pressed together to form a sandwich-structured cast feedstock. Thus, the apparatus of the invention is capable of recycling the wasted metal products efficiently.
The apparatus of the invention may comprise a crushing means for crushing the metal products and a separating means for separating the crushed metal products.
Preferably, the apparatus of the present invention further comprises a supplying means for supplying at least one content adjuster to the transport means. The content adjuster supplied to the transport means is mixed in the sandwich-structured cast feedstock.
In a third aspect of the present invention, a metal feedstock comprises cast blocks and sheet-shaped scraps wherein the cast blocks are disposed between the sheet-shaped scraps and pressed together to form a sandwich-structured metal feedstock. The cast feedstock is firmly bounded and heavy enough to fall in the cupola.